The present invention relates to a device (living body light measuring device) for irradiating a human head with light, measuring light reflected or scattered within the head near the surface (hereafter referred to also as living body transmitted light), and thereby measuring a higher brain function.
The living body light measuring device is a device for detecting living body transmitted light using light in the range of visible to near infrared rays, and measuring the living body function in a non-invasive manner. In recent years, living body light measuring devices for irradiating light from a plurality of positions by using optical fibers, measuring a living body transmitted light intensity at a plurality of detection points, obtaining information of a comparatively wide area including these detection points, and imaging the brain function have been developed. It is attempted to apply these living body light measuring devices to the study of the brain function and clinical use.
Information obtained in such a living body light measuring device is a signal corresponding to a change of a substance (such as hemoglobin) in blood between before and after a trial, when a stimulation or a task (trial) such as a language stimulation, a flash stimulation, or finger tapping is given mainly to a living body a plurality of times. Such a change signal of hemoglobin which is a substance in blood is displayed every measurement channel typically as a graph (signal waveform) indicating a time course or as an image called topography obtained by coupling values at measurement points in a contour line form.
As a result of accumulation of studies on relevancies between the signal waveform and the brain function, a living body light measuring device having a function of making a decision on brain diseases or mental diseases on the basis of a feature extracted from the signal waveform is also developed (US2005/0177033 corresponding to JP-A-2003-275191). Furthermore, a technique of conducting a quantitative analysis on the signal waveform and generating quantitative data is also proposed (JP-A-2002-177281). In US2005/0177033, a technique of representing a feature such as a peak value or a latency as a template on the basis of the measurement waveform of the hemoglobin signal, comparing a feature pattern of a healthy person with a feature pattern of a mental disease patient, and assisting in diagnosing a mental disease is disclosed.
Until now, brain function measurements using living body light measurement are based mainly on the relevancies between the change waveform of a substance in blood before and after the load such as stimulation and the brain function. In recent years, it has been found that the hemoglobin signal waveform is also changed by metabolism of substances in the living body. It is desired to develop a living body light measuring device capable of analyzing its physiological meaning and conducting display associated with parameters of the hemoglobin signal waveform. When alcohol intake is conducted, the hemoglobin waveform is changed according to a time curve of blood acetaldehyde concentration, which is an alcohol metabolic substance, or endocrine hormones, by the aldehyde dehydrogenase 2 genotype concerning aldehyde dehydrogenase. This phenomenon is reported.
In the conventional living body light measuring device, the hemoglobin signal waveform which is measurement data is displayed only as a time course, an average value, or a topography. A hemoglobin signal waveform relating to a time curve of a metabolic substance cannot be monitored.
Parameters (features) representing the hemoglobin signal waveform are considered to have relevancies to various physiological reactions. In the conventional living body light measuring device, however, it is not possible to analyze these relevancies and judge characteristic traits of a specific testee on the basis of a result of the analysis.